The present invention relates to a position detecting system which is intended to be applied chiefly to harness frames in a weaving machine.
In an arrangement of a negative type weaving machine, a shedding motion means functions to move the harness frame in one of the upward and downward directions, a pulling means serves to draw the harness frame in the other direction. The shedding motion means and the pulling means are respectively connected to the harness frame through connecting wires.
The connecting wires between the shedding motion means and the harness frame inevitably become gradually slackened in their tension if the weaving machine is operated over a long period of time. This causes the shedding motion means to fail to achieve a predetermined amount of warp shedding, and any resulting sheds in the warps are decreased in size, while at the same time, the other connecting wires are also reduced in their tension.
The foregoing decrease in the warp shedding amount causes a weft to be easily caught in the warps as it is being fed through the sheds formed between the upwardly lifted warps or the downwardly lowered warps and the other warps. This results in a disadvantage of the conventional negative type weaving machines, in which defective products can easily be produced.
Also, the foregoing reduction in the tension of the connecting wires between the shedding motion means and the harness frame and between the pulling means and the harness frame causes the harness frame to fluctuate easily, and if the harness frame fluctuates, the rod eyes located at the upper and lower end portions of the heddles are easily damaged, because the upper and lower edge portions of the harness frame are inserted through the rod eyes via the rods. This is another disadvantage of the conventional negative type weaving machines.
Moreover, fluctuation of the harness frame results also in a disadvantage in which the connecting wires and the eyes or mails of the heddles through which the warps are inserted to lift or lower the warps to form the sheds in them can easily be damaged, and this causes the warp to be readily cut. This disadvantage is still more likely to occur if both connecting wires connected from the shedding motion means to the right hand side and left hand side lower or upper end portions of the harness frame do not have an equivalent amount of slack.
Substantially all of the weaving machines recently in operation are of the high-speed operation type. Such high-speed operation type weaving machines are inevitably especially affected by the foregoing disadvantages.
If the connecting wires between the shedding motion means and the harness frame become slackened in their tension, the foregoing disadvantages are unavoidable. The occurrence of slack in the connecting wires is also substantially inevitable in the negative type weaving machines. Therefore, it will occasionally become necessary to adjust the working length of the connection wires between the harness frame and the shedding motion means to regulate the level of the harness frame, such as described in, for example, German Auslegeschrift De-A 35 33 336 and also German Auslegeschrift DE-A 35 36 868.
In the foregoing prior art references, however, while mention is made of the necessity of reducing the slack in the connecting wires, no means is disclosed which allows the slack of the connecting wires to be detected. This is true of other conventional weaving machines. That is to say, in the conventional type weaving machines, when the connecting wires from the shedding motion means to the harness frames slacken, it is difficult or impossible to find or know the slack of the connecting wires, and the weaving machines were continuously operated with the slackened connecting wires, thereby resulting in the foregoing disadvantages.